The origin of 120 jiazi

Answer: Why do you say 120 Jiazi? It should be said that 120 Jiazi means two 60-year Jiazi years. There is a Jiazi year every 60 years, and 120 has two Jiazi years. According to the Book of Changes, the combination of ten heavenly stems and twelve earthly branches into a sixty-flower armor is called one yuan, two sixty-flower armor is called two yuan, and two yuan is 120 and 180 is called three yuan. There is a saying that according to Jin Mu's five elements, it will be shipped every 20 years in 180.